Starter pinion with molded base and drive

ABSTRACT

A starter pinion assembly for use with electric starters for internal combustion engines wherein a starter pinion gear is axially displaced upon a drive shaft during initial rotation of the shaft to engage the pinion gear with an engine flywheel in order to crank the flywheel. The starter pinion includes a hub portion upon which the pinion gear teeth are mounted, the pinion gear teeth being capable of rotation relative to the hub portion, and resilient frictional drive means are interposed between the hub and toothed gear portion through which torsional forces are transmitted. Axial forces imposed upon the hub maintain an effective frictional drive connection with the toothed gear portion, and impact and shock forces are absorbed. A stop mounted upon the drive shaft limits axial movement of the starter pinion assembly, and a compression spring maintains the starter assembly in the &#39;&#39;&#39;&#39;retracted&#39;&#39;&#39;&#39; position when the drive shaft is not being rotated. The resilient drive means prevents binding of the pinion assembly with the stop. A resilient bumper mounted upon the starter assembly, formed of the friction material, absorbs axial movement of the starter assembly toward the noncranking position, brakes the pinion assembly against rotation and also functions as a dust seal.

United States Patent 91 Primary ExaminerG. R. Simmons, Attorney, Agent,or Firm-Beaman &'Beaman Hamman Feb. 12, 1974 STARTER PINION WITH MOLDEDBASE [57] ABSTRACT AND DRIVE A starter pinion assembly for use withelectric starters [75] Inventor: Lyle J. l-lamman, Eaton Rapids, forinternal combustion engines wherein a starter pin- Mich. ion gear isaxially displaced upon a drive shaft during initial rotation of theshaft to engage the pinion gear [73] Asslgnee' Stawpmg Company Eatonwith an engine flywheel in order to crank the flywheel.

, Rapids Mich The starter pinion includes a hub portion upon which [22]Filed: Aug. 24, 1972 the pinion gear teeth are mounted, the pinion gearteeth being capable of rotation relative to the hub por- [21] Appl'283560 tion, and resilient frictional drive means are interposed betweenthe hub and toothed gear portion [52] US. Cl 290/38, 290/37, 290/48through which torsional forces are transmitted. Axial [51] Int. Cl. F02n11/00 forces imposed upon the hub maintain an effective [58] Field ofSearch... 310/254, 258, 259, 179, 180; frictional drive connection withthe toothed gear por- 290/37, 38, 48; 123/179 tion, and impact and shockforces are absorbed. A

' 3 stop mounted upon the drive shaft limits axial move- [56] ReferencesCited ment of the starter pinion assembly, and a compres- UNITED STATESPATENTS sion spring maintains the starter assembly in the re- 2,944,4277/1960 Antonidis 61; a1. 290/38 x acted when.the drive Shaft is not i3,177,368 4/1965 Seilly 290/38 tatedj T resllem means i? bmdmg of231L653 10/1957 Brainardm 310/258 X the pinion assembly with the stop. Aresilient bumper 3,062,966 11/1962 Merrian 290/38 mounted p the Starterassembly. formed Of the 3,084,561 4/1963 Mattson.... 290/38 X frictionmaterial, absorbs axial movement of the 2,818,735 l/l958 Sabatini 290/38X starter assembly toward the noncranking position,

brakes the pinion assembly against rotation and also functions as a dustseal.

15 Claims, 4 Drawing Figures STARTER PINION WITH MOLDED BASE AND DRIVEREFERENCE TO RELATED APPLICATIONS This application is directed toelectric starter apparatus also disclosed in my copending U.S.application Ser. No. 283,559 filed Aug. 24, 1972.

BACKGROUND OF THE INVENTION The invention pertains to electric starterapparatus for internal combustion engines utilizing pinion gears axiallydisplaceable upon a drive shaft.

Many electric starters for internal combustion engines use Bendix typeapparatus wherein a pinion gear is axially displaceable upon a driveshaft rotated by an electric motor. Initial rotation of the drive shaftaxially moves the pinion gear upon the shaft for engagement with gearteeth formed on the engine flywheel, wherein the flywheel is rotated andthe engine cranked for starting purposes. Such Bendix type starters havebeen constructed in a wide variety of mechanical variations, and thebasic principles have proven acceptable for the function designed.

While Bendix type starters have been constructed utilizing shockabsorbing features, those arrangements presently available arerelatively expensive, and are not readily incorporable into conciseapparatus which is adapatable for use with small electric starters andsmall internal combustion engines, such as used on lawn mowers and thelike. Prior art electric starters using cushioning devices are shown inUS. Pat. Nos. 1,876,642; 1,955,110; 2,271,216 and 2,876,644, andstarters such as those shown in these patents do not meet theaforementioned prerequisites for electric starters for use with smallengines.

In an economical electric starter construction the number of componentsmust be minimized, and the interrelationship between operatingcomponents must be as simple and dependable as possible. Electricstarters mounted upon small internal combustion engines are subjected toextensive vibration forces, and considerable wear will occur between thestarter components due to such vibration, even when the starter itselfis not energized. The relationship of components, and the multiplicityof components of electric starters of the prior art seriously affect theeconomics of manufacturing and dependability of operation of priorconstructions.

BRIEF DESCRIPTION OF THE INVENTION It is an object of the invention toprovide a starter pinion assembly for electric starters, particularlyelectric starters used with small internal combustion engines such asused on lawn mowers, garden tractors, and the like. The starter assemblyof the invention utilizesa minimum of components, components which areeconomically manufactured, dependable in operation, and the entireassembly is of a concise configuration occupying a minimum of space, andrequires a minimum of clearance for association with engine components.

The starter assembly includes a hub member and a toothed pinion gearmember mounted upon a thread formed on a drive shaft. The pinion memberis rotatably mounted upon the hub member, and both members includeradially extending opposed surfaces between which a friction, torquetransmitting, resilient material is interposed.

The relationship of the radial flange defined upon the hub which is inopposed relation to a radially opposed surface on the pinion gearbetween which the friction and shock absorbing material is related issuch that as the pinion gear is axially moved into alignment with theengine flywheel for engine cranking purposes, the resistance of rotationof the pinion gear during cranking and engagement of the gear with astop causes a compression of the friction material. Thus, the higher thetorque requirements during engine cranking, the greater the frictionalengagement between the hub and pinion gear components insuring that thenecessary torque be transmitted to the pinion gear. The resilientmaterial produces a reverse torque which prevents binding of the gearand its stop and its ability to compress aids in aligning the piniongear teeth with the flywheel teeth of the engine to be started.

The drive shaft upon which the starter pinion is mounted is of acantilever form and includes a stop member located near the shaft end. Acompression spring is interposed between the stop member and the piniongear which biases the pinion gear assembly towards its normal ornoncranking position. A stop sleeve is defined upon the pinion gear toenclose the spring, yet not interfere therewith, and a cover memberencloses the spring, stop sleeve and stop member to protect thesecomponents.

In accord with the concept of the invention the friction and shockabsorbing material is bonded to the pinion gear, and is of a resilientmaterial, such as rubber, or the like, and includes an axially extendingportion which serves as a bumper and a brake for engaging the motorhousing when the starter pinion assembly is moved to its extremeposition toward the motor housing. Thus, upon the engine starting, androtating the pinion gear in a direction which disengages the pinion gearfrom the flywheel gear teeth, this rapid axial movement of the piniongear assembly toward the engine housing is absorbed by the flexiblematerial bumper and the pinion gear rotation is frictionally braked.

BRIEF DESCRIPTION OF THE DRAWINGS The aforementioned objects andadvantages of the invention will be appreciated from the followingdescription and accompanying drawings wherein:

FIG. 1 is an elevational view of a pinion gear starter assembly, andelectric starter motor, as related to an engine flywheel, the crankingposition of the pinion gear assembly being shown in dotted lines,

FIG. 2 is a sectional view of FIG. 1 as taken along Section IIIIthereof,

FIG. 3 is an exploded, perspective, detail view of starter assembly, and

FIG. 4 is a view similar to FIG. 2 illustrating the starter componentsin cranking relationship.

DESCRIPTION OF THE PREFERRED EMBODIMENT The starter pinion assemblystructure of the invention is used with an electric starter motor, suchas of the 12 volt DC or volt AC type. While the illustrated starterstructure was specifically designed for using with starting systems usedwith lawn mower size engines, it will be appreciated by those skilled inthe art that the concepts may be employed with starters for all sizes ofinternal combustion engines. However, the

concepts of the invention are particularly used to advantage withstarter systems for small engines.

In the drawings the electric motor is indicated at 10, and the motorincludes a housing 12 which may be mounted to the engine by mountingbracket 14 affixed to the housing. The housing 12 includes end caps 16and 18 having bearing structure for rotatably supporting the armature,generally indicated at 20.

The armature 20 includes a drive shaft extension 22, FIG. 2, which is ofa cantilever type, having a cylindrical portion received within end capbearing 24, and the end of the shaft extension is indicated at 26.

The drive shaft 22 is provided with a threaded portion 28 wherein thethreads are of a heavy duty multiple pitch type, and the shaft is of areduced diameter cylindrical configuration at 30, between the thread 28and the outer end 26.

A hub member 32 includes a threaded bore 34 which mates with the threads28, and the hub includes a radial flange 36, and an axially extendingcylindrical portion 38. The flange 36 is of a circular configuration,and includes a radial surface or face 40 facing the shaft end 26 andholes 41 extend through the flange in an axial direction.

The pinion gear 42 is rotatably mounted upon the hub portion 38, as thecylindrical bore 44 of the pinion is slightly larger than the hubportion 38. As will be noted in FIGS. 2 and 4, the diameter of thepinion bore is reduced at 46 whereby a close, but rotatable fit existsbetween the right end of the pinion, FIG. 2, and the shaft portion 30.The pinion gear 42 is provided with gear teeth 48, and is formed with anannular recessed groove 50 to aid in the attachment of the flexiblematerial thereto, as will be later described. The inner end of thepinion gear includes a radially extending face or surface 52 in opposedrelation to the flange surface 40. The right end of the pinion 42 isprovided with an annular abutment sleeve 54 having a lip 56 whereby theprotective cover 58, later described, may be attached to the piniongear.

A frictional shock absorbing member 60 of rubber, or similar syntheticresilient material, is molded upon the pinion 42, and is received withinthe groove 50, whereby the resilient material is firmly bonded to thepinion. The member 60 includes a recess 61 defining an annular innerextending lip 62 received between the surfaces 40 and 52 and this lip issubjected to compressive forces during cranking of the engine, as willbe described. The hub flange 36 snaps into recess 61 to maintain theassembly of the hub and pinion gear. The member 60 is of an enlargedthickness at its peripheral region, and is of such axial lengthextending tothe left, FIG. 2, that the leftmost edge 64 of the member isleft of the flange 36 whereby the edge 64 engages the housing end cap18, FIG. 2, when the starter pinion assembly is at the noncranking ornormal position illustrated in FIG. 2 for braking and dust sealpurposes.

The end of the shaft 22 is provided with a snap ring receiving groove66, and an annular stop member 68 is mounted upon the shaft end, and isretained in this position by the snap ring 70 cooperating with thegroove 66, and the bore of the stop member.

A compression spring 72 is interposed between the stop member 68, andthe right end of the pinion 42, FIGS. 2 and 4. The compression spring 72imposes a biasing force on the pinion toward the left, and the springnormally maintains the edge 64 of member 60 in engagement with thehousing end cap 18. The radial dimension of the stop member 68 issubstantially equal to the radial dimension of the stop sleeve lip 56,as will be appreciated from the drawing.

An annular cover 58, of synthetic material, is attached to the pinion 42by snapping the cover over the stop sleeve lip 56, and the cover 58encloses the shaft portion 30, the stop member 68, the stop sleeve andthe spring 72.

In operation, the components will initially be related as shown in solidlines in FIGS. 1 and 2. The pinion gear assembly will be at itsinnermost, at rest position due to the biasing force exerted by thespring 72, and in this position the pinion gear is out of alignment withthe engine flywheel 74 to be cranked, and the edge 64 is engaging endcap 18 keeping foreign matter out of the hub and shaft 22.

Upon energizing the motor 10 the rapid acceleration of the drive shaft22 will produce a relative rotation between the thread 28 and the hub 32causing axial movement of the hub, pinion gear 42 and member 60 to theright to produce a meshing of the pinion gear teeth 48 with the flywheelteeth 76, as represented by dotted lines in FIG. 1, and as shown in fulllines in FIG. 4. This movement of the pinion gear assembly to the rightcauses the right edge of the stop sleeve 54 to rapidly engage the stopmember 68 as shown in FIG. 4, and in this position the pinion gear teethare in full mesh with the flywheel teeth.

As the motor armature rotates, the hub 32 will be rotated in a directiontending to move the pinion gear 42 to the right. Of course, theengagement of the stop sleeve, with the stop 68, and the torque imposedupon the pinion gear causes the flange 36 to be forced against thefriction member lip 62 compressing this material and establishing aneffective frictional driving relationship between the flange and thepinion gear. This driving connection is enhanced by the holes 41, intowhich the lip material tends to extrude. Thus, the pinion gear 42 isrotatably driven through the lip 62, and the lip is highly compressedbetween the surfaces 40 and 52.

Upon the engine starting, the pinion 42 will be rotated faster by theflywheel 74, than the rate of rotation of the shaft 22 under theinfluence of the electric motor, and such condition rotates the piniongear, and hub 32 in the direction on the thread 28 moving the piniongear assembly to the left toward the housing end cap 18. This axialmovement of the hub member and pinion gear continues until the edge 64engages the end cap 18 as shown in FIG. 2. At this time the pinion gear42 will be out of engagement with the flywheel teeth 76, and the startermotor 10 is deenergized. The spring 72 will insure that the pinion geardoes not engage the flywheel until the starter motor is again energized.

The resilient and flexible nature of the material of member 60 servesseveral functions. First, the torque imposed on the lip 62 by the flange36 produces a torsional spring effect that prevents the pinion gear 42from locking or binding due to its engagement with stop member 68. Theresilience of the material of lip 62 produces a reverse torsion on thegear 42 after the gear engages the stop member which backs off the hub32 on the thread 28 slightly to prevent the gear from locking to thestop. Secondly, the material of lip 62 functions as a shock absorber andis able to slightly compress if the leading edge of gear teeth 48 engagethe edge of flywheel teeth 76 as the teeth seek alignment. This abilityof the lip to compress permits the gear teeth to align and mesh and thelip absorbs the shock of engagement of the misaligned teeth. Of course,the leading edge of teeth 48 are rounded and beveled to aid meshing. Thefact that the lip and flange may be dimensioned so as to radially liewithin the desired diametrical dimension of the pinion gear teeth 48,lends to the concise configuration of the starter pinion assembly, andthe construction minimizes the likelihood of foreign matter affectingthe frictional relationship between the starter components.

It is appreciated that various modifications to the inventive conceptmay be apparent to those skilled in the art without departing from thescope of the invention.

I claim:

1. An electric starter for starting an internal combustion enginecomprising, in combination, an electric motor having a housing and arotatable output shaft extending from said housing having an axis, saidshaft having an outer end and an inner portion disposed adjacent saidhousing, a hub rotatably mounted on said shaft, intermeshing cam meansformed on said shaft and said hub rotating said hub and producing axialmovement of said hub upon said shaft during relative rotation betweensaid hub and said shaft, a pinion gear concentrically mounted on saidshaft for rotational and axial movement thereon, stop means mounted onsaid shaft limiting axial movement of said gear toward said outer end,radially extending axially spaced opposed surfaces defined on said huband said gear, and resilient friction means interposed between said huband gear surfaces transmitting torque from said hub to said gear torotate said gear, said hub surface facing in the direction of axialmovement of said gear to engage said gear with engine starter structurewhereby said resilient means is compressed between said surfaces duringengine cranking.

2. In an electric starter as in claim 1 wherein said stop means ismounted on said shaft adjacent said outer end, and a compression springinterposed between said stop means and said gear biasing said geartoward said motor housing.

3. In an electric starter as in claim 1, a resilient shock absorbermounted on said gear engagable with said motor housing limiting axialmovement of said gear on said shaft toward said housing and brakingrotation of said gear with respect to said housing.

4. In an electric starter as in claim 1 whererin said resilient means ismolded upon said gear.

5. In an electric starter as in claim 4 wherein said resilient means andsaid shock absorber are defined by a homogeneous resilient elementmounted upon said gear.

6. In an electric starter as in claim 1 wherein said hub includes aradially extending flange and an axially extending cylindrical portion,said gear having a cylindrical bore engaging said axially extendingportion wherein said hub concentrically supports said gear on saidshaft.

7. In an electric starter as in claim 6 wherein said radially extendinghub surface is defined on said flange.

8. In an electric starter as in claim 1 wherein said cam means comprisesa screw thread defined on said shaft inner portion and a mating screwthread defined on said hub.

9. A pinion gear assembly for an electric starter for internalcombustion engines comprising, in combination, an annular hub having anaxis, a bore and a first radially extending surface, a gear mounted uponsaid hub for relative rotational and axial movement thereon, a secondradially extending surface defined upon said gear in opposed relation tosaid first surface, and resilient material interposed between saidsurfaces for transmitting torque forces between said hub and said gear.

10. In a pinion gear assembly as in claim 9 wherein said resilientmaterial is bonded to said gear.

11. In a pinion gear assembly as in claim 9, a screw thread defined insaid hub bore.

12. In an electric starter assembly, in combination, a rotatable driveshaft having an axis and first and second axially spaced portions, a hubrotatably mounted on said shaft first portion, engaging threads formedon said shaft first portion and said hub for rotating said hub andproducing axial movement of said hub upon said shaft during relativerotation between said hub and said shaft, a pinion gear rotatablymounted upon said hub and axially movable thereon, stop means mounted onsaid shaft second portion limiting axial movement of said hub and gearon said shaft, radially extending, axially spaced opposed surfacesdefined on said hub and said gear, and resilient friction materialinterposed between said hub and gear surfaces for transmitting torquefrom said hub to said gear, said hub surface facing in the axialdirection of movement of said hub and gear to operatively engage saidgear with engine starter structure.

13. In an electric starter assembly as in claim 12 wherein saidresilient material is bonded to said gear.

14. In an electric starter assembly as in claim 12, a compression springmounted on said shaft interposed between said stops means and said gearbiasing said gear toward said hub surface and said first shaft portion.

15. In an electric starter assembly as in claim 14, an annular covermounted on said gear encompassing said stop means and said spring.

1. An electric starter for starting an internal combustion engine comprising, in combination, an electric motor having a housing and a rotatable output shaft extending from said housing having an axis, said shaft having an outer end and an inner portion disposed adjacent said housing, a hub rotatably mounted on said shaft, intermeshing cam means formed on said shaft and said hub rotating said hub and producing axial movement of said hub upon said shaft during relative rotation between said hub and said shaft, a pinion gear concentrically mounted on said shaft for rotational and axial movement thereon, stop means mounted on said shaft limiting axial movement of said gear toward said outer end, radially extending axially spaced opposed surfaces defined on said hub and said gear, and resilient friction means interposed between said hub and gear surfaces transmitting torque from said hub to said gear to rotate said gear, said hub surface facing in the direction of axial movement of said gear to engage said gear with engine starter structure whereby said resilient means is compressed between said surfaces during engine cranking.
 2. In an electric starter as in claim 1 wherein said stop means is mounted on said shaft adjacent said outer end, and a compression spring interposed between said stop means and said gear biasing said gear toward said motor housing.
 3. In an electric starter as in claim 1, a resilient shock absorber mounted on said gear engagable with said motor housing limiting axial movement of said gear on said shaft toward said housing and braking rotation of said gear with respect to said housing.
 4. In an electric starter as in claim 1 whererin said resilient means is molded upon said gear.
 5. In an electric starter as in claim 4 wherein said resilient means and said shock absorber are defined by a homogeneous resilient element mounted upon said gear.
 6. In an electric starter as in claim 1 wherein said hub includes a radially extending flange and an axially extending cylindrical portion, said gear having a cylindrical bore engaging said axially extending portion wherein said hub concentrically supports said gear on said shaft.
 7. In an electric starter as in claim 6 wherein said radially extending hub surface is defined on said flange.
 8. In an electric starter as in claim 1 wherein said cam means comprises a screw thread defined on said shaft inner portion and a mating screw thread defined on said hub.
 9. A pinion gear assembly for an electric starter for internal combustion engines comprising, in combination, an annular hub having an axis, a bore and a first radially extending surface, a gear mounted upon said hub for relative rotational and axial movement thereon, a second radially extending surface defined upon said gear in opposed relation to said first surface, and resilient material interposed between said surfaces for transmitting torque forces between said hub and said gear.
 10. In a pinion gear assembly as in claim 9 wherein said resilient material is bonded to said gear.
 11. In a pinion gear assembly as in claim 9, a screw thread defined in said hub bore.
 12. In an electric starter assembly, in combination, a rotatable drive shaft having an axis and first and second axially spaced portions, a hub rotatably mounted on said shaft first portion, engaging threads formed on said shaft first portion and said hub for rotating said hub and producing axial movement of said hub upon said shaft during relative rotation between said hub and said shaft, a pinion gear rotatably mounted upon said hub and axially movable thereon, stop means mounted on said shaft second portion limiting axial movement of said hub and gear on said shaft, radially extending, axially spaced opposed surfaces defined on said hub and said gear, and resilient friction material interposed between said hub and gear surfaces for transmItting torque from said hub to said gear, said hub surface facing in the axial direction of movement of said hub and gear to operatively engage said gear with engine starter structure.
 13. In an electric starter assembly as in claim 12 wherein said resilient material is bonded to said gear.
 14. In an electric starter assembly as in claim 12, a compression spring mounted on said shaft interposed between said stops means and said gear biasing said gear toward said hub surface and said first shaft portion.
 15. In an electric starter assembly as in claim 14, an annular cover mounted on said gear encompassing said stop means and said spring. 